Ore concentration



Patented Jan. l 5, 1946 ORE CONCENTRATION Herbert S. Woodward and William- A. Bates, Gabbs, Nev., assignors, by mesne assignments, 11:1; Defense Plant Corporation, Washington.

No Drawing. Application May 9, 1944, Serial No. 534,811

12 Claims. (Cl. 209-166) This invention relates to the beneflciation of magnesium-bearing ores, especially magnesite, and has for its object the separation of magnesite from its accompanying impurities in the ore by froth flotation. More particularly, the invention provides an improved method of separating siliceous materials from magnesite by froth flotation in an economical and eflicient operation.

Magnesites occurring in nature commonly have associated with them objectionable quantities of siliceous impurities, such as tales and serpentines. Such impurities reduce the value of the ore, or limit its usage, for the manufacture of magnesium metal and refractory materials. In the beneflciation of magnesite, it is customary selectively to mine and sort or screen the ore to eliminate the low-grade material and associated gangue. Several froth flotation processes have been proposed for concentrating magnesite ores, involving the use of cationic collectors and methyl amyl alcohol to float the siliceous impurities, and the use of naphthenic acids for floating magnesite, utilizing other reagents to depress the siliceous and calcareous components. The flotation of a talc concentrate from magnesite-containing gangue, using a wetting agent involving sodium or ammonium alkyl sulphates. has been suggested. Due tothe well-known floatability of the associated silica minerals, the direct flotation of magnesite from these impurities has failed to yield a product of suflicient purity for many industrial uses.

The proposed practices of floating the silicate impurities away ,from the magnesite either leave an undesirable amount of the silicate minerals with the residual magnesite fraction, or, in an attempt to obtain a magnesite fraction of low silica content, remove an undesirably large amount of the magnesite along with the siliceous froth, with resultant lower recoveries of magnesite and high operating cost. These proposed practices fail to recover a high magnesia product low in silica from ores containing in the neighborhood of or more of acid insoluble material, and, for the most part, have the economic disadvantage that they require relatively large quantities of expensive reagents and, in many instances, require the preliminary removal of slimes in order to obtain a high-grade product and to reduce the reagent consumption to a practical basis. The removal ofslimes further lowers the recovery and'increases the cost of the recovered magnesite. i

It .is an object of this invention to overcome the disadvantages of. the practices proposed heretoi'ore andto provide an improved method for a magnesite product low in silica.

Based upon our discoveries, the invention provides an improved method of separating a relathe economical separation by'froth flotation of tively pure magnesite from 'ore containing siliceous impurities by froth flotation, involving the incorporation in a pulp of the ore a reagent comprising saturated aliphatic monocarboxylic acids,

. the esters of such acids, or mixtures of such acids and esters for the floating of siliceous impurities.

The invention is advantageously applicable to the treatment of low-grade magnesite ores which are difficult to handle by present flotation procedure. An example of such ores is the large, massive magnesite deposits located in northern Nye County, Nevada. Such ores contain variable proportions of siliceous impurities, including talcs, serpentines and fosterites. These magnesite ores may have associated magnesium minerals, such as brucite and hydromagnesite, and in places may have undesirably large amounts of R203 contaminants. While some of the siliceous and other impurities are present in relatively coarse aggregates, it is usually necessary to grind the ore to suitable fineness, for example, to approximately minus mesh, to free the impurities from the associated magnesite.

In practicing. the invention, the ore is first ground to a suitable degree of fineness and the ore, either during Or after grinding, is mixed with water to form a free-flowing pulp. The ore is preferably comminuted by wet grinding in a closed circuit with a classifier. The flotation reagents may be introduced into the grinding circuit, or they may be added in a separate conditioning treatment between the grinding and flotation circuits. Alternatively, the reagents may be added immediately ahead of the flotation circuit. In using a collector reagent in accordanc with the invention, we may use mixed aliphatic acids obtained from petroleum, and preferably having a boiling range between and 250 C. Such aliphatic acids are especially desirable from a standpoint of cost and their effective selective action in the floating of siliceous impurities. We may also use very effectively saturated aliphatic monocarboxylic acids containing from 4 to 9 carbon atoms, such as butyric and ethyl caproic acids, as reagents. Alternatively, esters made by reacting saturated aliphatic monocarboxylic acids having from 4'to 9 carbon atoms with saturated aliphatic alcohols may be used as reagents- Examples of such esters are methyl amyl butyrate, ethyl hexyl butyrateand the methyl isobutyl ester of 2-ethyl caproic acids. As a collector reagent we may also use mixtures of such aliphatic acids obtained from petroleum, saturated aliphatic monocarboxylic acids, and

' esters made by reacting saturated aliphatic monocarboxylic acids having from 4, to 9 carbon atoms with saturated aliphatic alcohols Anexample of such a mixture consists of 75% mixed aliphatic acids obtained from petroleum and 25% of 2- ethyl caproic acid; The esters formed by react- I jected to a further flotation treatment.

carried to the surface in a froth, where they may be removed. The'residual magnesite pulp, substantially impoverished. in siliceous impurities, may be dewatered and used as a source of magnesia for the production of magnesium metal or magnesia refractories, or other magnesian products requiring a low-silica material or the residual magnesite pulp may be treated by flotation or chemical processes further to remove associated siliceous and calcareous impurities from the magnesia product. For example, the residual magnesite pulp may be subjected to a second froth flotation treatment for selectively floating of the magnesite which is removed as a froth. The magnesite thus impoverished in calcareous contaminants is removed from the operation, dewatered and used. as a source of magnesia in the production of magnesium or magnesian products.

In the following illustrative examples of the present invention, magnesite ore from Nye County, Nevada, was used.

Example I Analysis, percent Percent Product of feed Add in Soluble R10: 080

Feed... 100. 0 5. 45 2. B 9. 40 Froth concentrste ll. 90 35. 46 2. l7 7. 47 Taillng (magnesite) 88.10 1.41 2.29 9.66

The magnesite enriched tailing was then sub- The magnesite was selectively floated in this operation and taken oi! as a rougher concentrate, which was recleaned. The results of this test are shown below:

Magnesite pulp ground to pass approximately l00-mesh sieve was conditioned with appro imately 0.3 pound or mixed aliphatic acids obtained from petroleum per ton of ore. The conditioned pulp was subjected to froth flotation and the following products were obtained:

Analysis, percent Percent Product of mad Add insoluble 0B0 Feed.. 100.0 5.54 2. 19 1.00 Froth conccntrate 0.10 45. l7 1. 72 6. 50 Telling (msgnesite) 90. 9 l. 57 2. 23 10.35

The magnesite tailing resulting from this flotation step was subjected to an additional flotation treatment to reduce the lime content of the magnesite. A rougher concentrate was floated and recleaned. The results of the second flotation were as follows:

Analysis, percent Percent Product of original A m insoluble C80 Cleaner eoncentrate..-. 64.50 0. 50 0:63 7.50 Cleaner tailing.-." l2. 4 2. 67 2. 77 i6. Rough concentrate--- 77. 0 0. 85 0. 97 9. 32 Rougher tailing 13.0 5. 6i 0. 75 i6. 00

Example III Wet-ground magnesite pulp passing approximately 100-mesh sieve was conditioned with approximately 0.3 pound per ton of methyl amyl butyrate and a siliceous froth was removed. The

results 01'- this test were as follows:

Analysis. percent Percent Product dread Add insoluble C30 Feed 100.0 5.50 3.07 0.75 Froth concentration.-." 6.76 57.88 i. 20 4. Telling (magncsite) 93.24 1. 6i 2. 47 l0. 10

The tailingfrom this test was subjected to a second froth flotation treatment wherein the magnesite fraction was floated and the calcareous material was depressed.

Example IV The magnesite pulp, wet-ground to p ss approximately -mesh sieve, was conditioned with 0.3 pound of butyrlc acid per ton of ore and with 0.15 pound pine oil per ton of ore. The insoluble impurities were collected in a froth concentrate with the following results:

Analysis, percent Percent I Product of feed Add insoluble CB0 100. 0 5. 44 2. 25 9. 60 From conccntratc. 8. 35 49. 01 l. 81 6. l0 Telling (magncsite) 01.65 1. 57 2. 30 9. 02

atoms, esters made by reacting saturated aliphatic monocarboxylic acids having from 4 to 9 carbon atoms with saturated aliphatic alcohols, and mixtures of such mixed aliphatic acids obtained from petroleum, saturated aliphatic monocarboxylic acids having from 4 to 9 carbon atoms and esters made by reacting saturated aliphatic monocarboxylic acids having from 4 to 9 carbon atoms with saturated aliphatic alcohols and any other desired quantities of these reagents may be used in treating such ores depending upon the conditions of treatment and the results sought. The particular quantity of reagent will depend upo such factors as the character of the ore, the physical characteristics of the pulp, the degree of conditioning used and the quality of the reagent employed. The magnesite product resulting from the first flotation step may be further beneficia'ted by calcining the magnesite and removing the lime by chemical methods.

We claim:

1. In the froth flotation separation of magnesite from siliceous impurities contained in ore, the improved method which comprises incorporating in a pulp of the ore a collector reagent comprising mixed aliphatic acids obtained from petroleum and having a boiling range of from 160 to 250 C., subjecting the pulp to a flotation treatment and selectively separating siliceous impurities as a froth from the magnesite.

2. In the froth flotation separation of magnesite from siliceous impurities contained in ore, the improved method which comprises incorporating in a pulp of the ore a collector reagent comprising a saturated monocarboxylic aliphatic acid having from 4 to 9 carbon atoms, subjecting the pulp to a flotation treatment and selectively separating siliceous impurities a a froth from the magnesite.

3. In the froth flotation separation of magnesite from siliceous impurities contained in ore, the improved method which comprises incorporating in a pulp of the ore a collector reagent comprising an ester formed by reacting a saturated aliphatic monocarboxylic acid having from 4 to 9 carbon atoms with a saturated aliphatic alcohol, subjecting the pulp to a flotation treatment and selectively separating siliceous impurities as a froth from the magnesite.

4. In the froth flotation separation of magnesite from siliceous impurities contained in ore, the improved method which comprises incorporating in a pulp of the ore a collector reagent comprising a. mixture of saturated aliphatic acids obtained from petroleum, and an ester formed by reacting saturated aliphatic monocarboxylic acid having from 4 to 9 carbon atoms with a saturated aliphatic alcohol, subjecting the pulp to a flotation treatment and selectively separating siliceous impurities as a. froth from the magnesite.

5. In the froth flotation separation of magnesite from siliceous impurities contained in ore, the improved method which comprises incorporating in a. pulp of the ore a collectorereagent comprising butyricacid, subjecting the pulp to a flotation treatment and selectively separating siliceous impurities as a froth from the magnesite.

6. In the froth flotation separation of magnesite from siliceous impurities contained in ore, the improved method which comprises incorporating in a pulp of the ore a collector reagent comprising methyl amyl butyrate, subjecting the pulp to a flotation treatment and selectively separating siliceous impurities as a froth from the magnesite.

7. In the froth flotation separation of magnesite from siliceous and calcareous impurities contained in ore, the improved method which comprises incorporating in a pulp of the ore a collector reagent comprising a saturated monocarboxylic aliphatic acid having from 4 to 9 carbon atoms, and subjecting the pulp to a flotation treatment and selectively separating siliceous impurities as a froth from the magnesite.

8. In the froth flotation separation of magnesite from siliceous impurities contained in ore, the improved method which comprises incorporating in a pulp of the ore a collector reagent comprising an ester formed by reacting a saturated aliphatic monocarboxylic acid having from 4 to 9 carbon atoms with a saturated aliphatic monohydric alcohol, subjecting the pulp to a flotation treatment and selectively separating siliceous impurities as a froth from the magnesite.

9. In a froth flotation separation of magnesite from siliceous impurities contained in ore, the improved method which comprises incorporating in a pulp of the ore a collector reagent comprising an ester formed by reacting a saturated aliphatic monocarboxylic acid having from 4 to 9 carbon atoms with a saturated aliphatic primary monohydric alcohol, subjecting the pulp to a flotation treatment and selectively separating siliceous impurities as a froth from the magnesite.

10. In the froth flotation separation of magnesite from siliceous impurities contained in ore, the improved method which comprises incorporating in a pulp of the ore a collector reagent comprising a mixture of saturated aliphatic acids obtained from petroleum and an ester formed by reacting saturated aliphatic monocarboxylic acid having from 4 to 9 carbon atoms with a saturated aliphatic monohydric alcohol, subjecting the pulp to a flotation treatment and selectively separating siliceous impurities as a froth from the magnesite.

11. In the froth flotation separation of magnesite from siliceous impurities contained in ore, the improved method which comprises incorporating in a pulp of the ore a collector reagent comprising a mixture of saturated aliphatic acids obtained from petroleum and an ester formed by reacting saturated aliphatic monocarboxylic acid having from 4 to 9 carbon atoms with a saturated aliphatic primary monohydric alcohol, subjecting the pulp to a flotation treatment and selectively separating siliceous impurities as a froth from the magnesite.

12. In the froth flotation separation of magnesite from siliceous impurities contained in ore, in which pine oil is used as a frothing agent, the improved method which comprises incorporating in a pulp of the ore a collector reagent comprising butyric acid, subjecting the pulp to a flotation treatment and selectively separating siliceous impurities as a froth from the magnesite.

HERBERT S. WOODWARD. WILLIAM A. BATES. 

